5 Local Area Network (LAN)A network serving a home, building or campus is called a Local Area Network (LAN)Modern switch-based LANs usually have a star topology whereas older hub-based LANs were organized in a bus structure.

6 Wide Area Network (WAN)failureLANs separated by geographic distance are connected by a network known as a Wide Area Network (WAN)WANs usually have a point-to-point or ring topologyThe logical topology can be different from the physical one!

7 InternetThe Internet is defined as a global mesh of interconnected networks

9 Shared Network CommunicationData is sent across a network in small “chunks” called segmentsSegmentationMessages or data streams are split up into segmentsMultiplexingMultiple users share the same communication channel

12 Role of Intermediary Devices IIIntermediary network devices perform the following functions:Regenerate and retransmit the data signalMaintain information about the pathways existing through the network and internetworkNotify other devices of errors and communication failuresDirect data along alternate pathways in the event of a link failureClassify and direct messages according to Quality-of Service prioritiesPermit or deny the flow of data based on security settings

15 Function of a Network ProtocolNetwork protocols are used to allow hosts or devices to communicate successfullyProtocols provide:The format or structure of the messageThe process by which networking devices share information about pathways to other networksHow and when error and system messages are passed between devicesThe setting up and termination of communication sessions

16 Protocol Suites and Industry StandardsA standard is a process or protocol that has been endorsed by the networking industry and ratified by a standards organization.A protocol suite is a collection of protocols.Standards Organizations:IEEE - Institute of Electrical and Electronics EngineersIETF - Internet Engineering Task ForceITU - International Telecommunications Union

17 Technology Independent ProtocolsDiverse types of devices can communicate using the same sets of protocols. This is because network protocols specify network functionality, but not the underlying technology required to support this functionality.

38 TCP/IP Reference ModelDeveloped by the Advanced Research Projects Agency (ARPA) of the U.S. Department of Defence (DoD)

39 Comparing the OSI and TCP/IP ModelsTCP/IP combines the upper three layers of the OSI model into a single Application Layer.Part of the OSI Session Layer (e.g. session management) has been integrated into the [TCP] Transport Layer.TCP/IP combines the lower two layers of the OSI model into a single Network Access Layer